It is often desirable to fill the cavity sections of assemblies with low density materials to obtain acoustic damping, structural reinforcement or sealing.
Various expandable foam materials are known in the art. For instance, it is known to have a foam filled article comprising a polymeric outer shell and a foam core. It is prepared by compressing expandable material in a degradable container, then forming a shell while degrading the container. The foam may be expandable urethane, the degradable (e.g., by heat) container, a polyethylene bag and the shell, a vinyl polymer. When the container degrades during the forming of the shell, the unconstrained foam expands to fill the molded article. The need for the degradable bag, however, is time and cost ineffective and the degraded material is unwanted and perhaps otherwise detrimental.
It is also known to have a heat insulating material utilizing a core of polyurethane foam within a gas barrier material. Because of its deformability it is said that it can be used to insulate an irregular surface for excellent thermal insulation.
It is further known to have an expansion molded article comprising a porous sheet of a heat-resistant polymer which is bonded to a mold, in which are contained prefoamed particles to be uniformly heated.
Also known are various fillers for cavities including pillars and other automobile frame hollow structures used in the automotive industry. Typical filler materials are one- and two-part epoxies and polyurethanes that expand upon heating due to chemical reaction or chemical decomposition of a blowing agent. However, polyurethanes contain toxic isocyanates and many epoxy curing agents are allergic sensitizers, which require at least minimum handling precautions involving gloves and ventilation.
There exists, then, a need for a filler material which is efficiently and inexpensively capable of filling and bonding to the internal area of a cavity, and which works on a physical, rather than a chemical mechanism.